Photographic line printing



Feb. 5, 1935; K, u cK A 1,989,879

PHOTOGRAPHIC LINE PRINTING Filed Jan: 19, 1932 s NsmzEo EMULSION.

FLEXIBLE BASE MATERIAL 600/ As TRACING CLOTH.

FIRST COATING OF A cELLuLosE sEcoMo COATING OF'A DERWATIVE AND A PLASTlClZlNG coLorzLEss INERT POWDER,

AGENT. A PLASTICIZING AGENT/1ND A SOLVE NT- INVENTOR v ATTORNEY A PatentedFeb. 5, 1935 UNITED STATES PHOTOGBAPHIC LINE PRINTING Knud Murck, Forest Hills, N. Y., assignor to Charles Bruning Company Inc., a corporation 01' New York Application January 19, 1992, Serial No. 587,609

ficlaims.

This invention relatesto improvements in processes for preparing suitable flexible base materials such as ordinary commercial standard tracing cloth' for use in photographically reproducing 5 thereon tracings and drawings. Such reproductions are usually called black line prints on tracing cloth, the latter material being the one most commonly used. The object of the invention is to provide a superior sensitized tracing cloth as an article of manufacture whereby a more perfect dull surface is obtained for the use of ink or pencil on the finished print for purposes of alterations or additions thereto, and whereby the printed lines will adhere more closely to the tracing cloth and can only be removed with difiiculty. Another object of the invention is to provide a novel process for black line photographic printing on tracing cloth. The term tracing cloth will be used herein as a convenient designation of the flexible base material.

The usual methods of making prints on tracing cloth include waterproofing the cloth before sensitizing, then printing and developing. Some of these methods or processes do not result in en- .tirely satisfactory prints. Often the surface of the finished print is found to be more or less glazed thus rendering the use of ink or pencil thereon difiicult. In some cases it has also been found that the printed lines are too easily removed waterproofing coatings and. obtaining a clearerv and more beautiful finished print having an even dull and smooth surface which readily takes ink 40 or pencil marks. Concerning the use of the wordglaze, it is to be observed that the object of the pre-sensitizing or second coating is not primarily to destroy the glaze which commonly appears or is present in the waterproofing coating. The lat ter may not result in an objectionable glaze. But inasmuch as the waterproofing coating in and of itself repels to a greater or lesser degree the sensitizing coating, the second coating is em- 'ployed or put an to destroy this repellent actien 50 It the latter results in a glaze, then of the glaze is destroyed, but the glaze is merely a symptom or surface indication of-the waterproofing.

The accompanying drawing illustrates diagram-- 65 matically the invention-herein. The novel treator feature inherent in the waterproo seating.

ment also causes the printed lines to adhere far more closely to the tracing cloth surface.

In carrying out this invention the procedure is as follows: Ordinary tracing cloth is coated on one or both sides with a coating of suitable 6 waterproofing solution which is deposited on the tracing cloth in the form of a film. Any suitable apparatus may be used for this purpose. For instance, the tracing cloth may be passed through a bath. Thereafter the tracing cloth is dried in 10 a 'suitable drying apparatus. The waterproof solution dries on the tracing cloth into a uniform, glossy, transparent film on each side 'of the cloth.

The waterproofing solution may bemade according to the following formula: 1

Dibutyl phthalate 19 lbs. '8 oz. Butyl propionate 14 lbs. 8 oz. Ethyl lactate 8 lbs. 12 oz. Buta 3 lbs. 8 oz. w Lacquer 50 gallons Acetone 24 gallons acetates, diethyl carbonate, ethyl butyrate, amyl alcohol, toluol, or other known medium boilers or mixtures thereof.

Lacquer is a low-viscosity nitrocotton in acetone solution, the viscosity of the solution being 117-125 as determined with a MacMichael vis- 40 'cosimeter.

It may be replaced by a solution of cellulose acetate.

Acetone is a low-boiling solvent, and may be replaced wholly or partially by methyl or ethyl acetates, ethyl propionate, anhydrous ethyl alcohol, isopropyl alcohol, methanol, benzol, dichlor methane, or other known low-boilers or mixturesthereof.

form coating to the cloth on one time thereof.

Thereafter the dry waterproofed tracing cloth 5 The treating solution is made from a paste of the following typical composition.

Superfloss -e 12 oz. Dibutyl phthalate 1 lb. 2 oz. Alcohol (Formula 30) 1 pint finely-ground siliceous powders, diatomaceousearth, kieselguhr, tripoli, silicagel, barium sulfate, or other suitable inert powders or mixtures thereof.

Dibutyl phthalate is plasticizer, and has already been referred to.

Alcohol (Formula 30) is specially denatured alcohol, made by adding 10 gallons of methanol to 100 gallons of ethyl alcohol.

The effect of this treatment is to exert a mild solvent action on the waterproof film to the extent of destroying its glossy finish and then upon drying to leave deposited on the surface a matte, but transparent, layer of re-deposited nitrocotton mixed with a fine inert solid powder and plasticizer, the two latter being derived from the treating mixture. The special treating solution has no chemical action on the waterproofing film; the action is physical. The treating solution partially dissolves the cellulose nitrate and dibutyl phthalate in the surface 'of the waterproof film and upon application of heat, the solvent alcohol evaporates, re-depositing this cellulose nitrate and dibutyl phthalate mixed with more dibutyl phthalate and superfloss from the treating solution.

The object of this treatment is to make the Waterproof surface of the cloth so receptive to the sensitizing solution that the printed line resulting therefrom can be erased or chipped off only with the greatest difficulty; and also to make the surface more receptive to ink and pencil.

Thereafter the treated face of the cloth is coated with a light sensitive emulsion, by passing it over a coating roller which in rotating dips into a tank of the emulsion and carries up and applies to the face of the cloth a thin, uniform layer of the emulsion. After this coating has been applied in this fashion, the cloth is dried by passage thru a drying box.

A typical formula for the sensitizing emulsion follows:

Glue 110 grams Potassium bichromate 12 Silver nitrate 90 Potassium chloride 40 The sensitized tracing cloth is now a finished article of manufacture which may be stored, shipped andused in the trade in the same manner as other similar sensitized layers are handled and used commercially.

The process thereafter of making a print is carried out as follows. The negative which is obtained in the usual manner is placed against the sensitized face of the tracing cloth, exposed to light and a print is made. Thereafter the print on the sensitized tracing cloth is washed with water to remove the sensitized coating from the unexposed portions of the print. That is, the

coating which was under the opaque portions of the negative is washed away. Swabbing with a wad of wet. absorbent cotton hastens this operation and insures its completeness. The next step in the process is the developing of the print which is done by placing the print in a developing bath which may consist of Sodium carbonate (soda ash) 4 oz. Sodium sulfite 4oz. Hydroquinone oz. Monomethylparaminophenol sulfate oz.

The latter chemical is sold under a variety of trade names such as metol, pictol, rhodol, and others.

After having been developed the print is again washed to remove all surplus developer and then dried.

The finished print is waterproof and the tracing cloth regains its natural appearance and characteristics. It is a black line positive print on tracing cloth having a superior appearance and all the characteristics of an ordinary tracing on tracing cloth.

I claim:

1. As a new article of manufacture, a flexible sensitized photographic line print sheet comprising a flexible base material; a coating thereon consisting of a cellulose derivative and a plasticizing agent; a second coating on said first coating, said second coating consisting of an inert powder and a plasticizing agent and a sensitizing coating on said second coating.

2. As a new article of manufacture, a flexible sensitized photographic line print sheet having a matte receptive surface comprising a flexible base material; a coating thereon consisting of a cellulose derivative and a plasticizing agent; a second coating on said first coating, said second coating consisting of an inert powder and a plasticizing agent and a sensitizing coating on said second coating.

3. As a new article of manufacture, a flexible sensitized photographic line print sheet comprising a flexible base material; a coating thereon consisting of a cellulose derivative and a plasticizing agent; a second coating on said first coating, said second coating consisting of an inert powder and a plasticizing agent and a sensitizing coating on said second coating consisting of a glue-bichromate mixture impregnated with a silver salt.

4. The method of preparing a suitable flexible base material for photographic line printing which consists in placing on said base material a first coating including a cellulose derivative and a plasticizing agent whereby'to waterproof the same; placing a second coating on the first coating, said second coating consisting of a colorless inert powder, a plasticizing agent and a solvent whereby to partially dissolve said first coating; applying heat to cause the said partially dissolved portion of the said first coating to be redeposited in admixture with the said inert powder and plasticizing agent to render said material receptive to a light sensitive coating and finally placing a light sensitive coating on said second coating.

5. The method of preparing a suitable flexible base material for photographic line printing which consists in placing on said base material ing, said second coating consisting of a colorless inert powder, a plasticizing agent and a solvent whereby to partially dissolve said first coat.- ing; applyin heat to cause the said partially dissolvedportionoithe saidfirstcoatingtobe redeposited in admixture with the said inert powder and plasticizing agent to render said material receptive to a light sensitive coating and finally placing on said second coating a light sensitive coating consisting 01 a glue-bichromate mixture impregnated with a silver salt.

6. The method of preparing a suitable flexible base material to receive a light sensitive coating for photographic line printing which consists in placing on said base'material a first coating including a cellulose derivative and a plasticising agent whereby to waterproof the same; placing a second coating on the first coating, said second coating consisting of a colorless inert powder, a plasticizing agent and a solvent whereby to partially dissolve saidiirst coating and applying heat to cause the said partially dissolved portion of the said first coating to be redeposited in admixture with the said inert powder and plasticizing agent.

. KNUD MURCK. 

